Electrical space discharge tube lead-in construction



y T. H. amass. JR 2,206,937

ELECTRICAL SPACE DISCHARGE TUBE LEAD-IN CONSTRUCTION Filed June 15, 1938 720MB BRIGGS JR. 47 5 I "wig PatentedJuly 9, 1940 UNITED STATES PATENT OFFICE.

ELECTRICAL SPACE DISCHARGE TUBE LEAD-IN CONSTRUCTION Thomas H. Briggs, Jr.,

Raytheon assignor to Production Newton, Mass., a corporation of Hills, Mass., Corporation,

Delaware Wellesley Application June 15, 1938, Serial No. 213,784 8 Claims. (Cl. 250 27.5

The present invention relates to a lead-in construction for an electrical space discharge tube,

temperature.

Electrical space discharge tubes are ordinarily made with a sealed envelope having electrical sealed through a glass wall therein trode and the wall of the container. found, however, that the thermal properties of this lead-in construction play a very important part of the operation and characteristics of the resulting tube structures. For example, in connection with cathodes, particularly of the indi- I have encountered in excessive amounts of heat being transferred thereis connected so as to eliminate previous difliculties.

A still further object is to eliminate the possibility of transfer of suflicierit heat from a hot electrode of large heat capacity to the glass wall of an envelope to such an extent as to facilitate electrolysis of the glass.

, anode 4, a cathode Upon this press is supported an 5, and a control grid 6 surrounding the cathode 5 and interposed between 3. The two anode standards 1 carry an upper insulating spacer 8 and a lower insulating spacer 9 rigidly secured to said standards.

are supported. The anode 4 is directly welded to the lead-in wires 1, while the grid 6 and the cathode 5 are supported from the insulating An electrical connection is made to the grid 6 by means of a lead-in wire l9 sealed in the press 3 of the side rods of said grid.

The cathode 5 consists of a hollow tubular metal member, preferably of nickel, carrying a coating l5 thereon of such as for example a mixture of barium and strontium oxide. The cathode is heated so that the coating i5 is raised to temperature of thermionic emission by means of a heater within the hollow tubular cathode member. This heater consists of a filament with the two ends H| l necting the lead-in wire l3 and the cathode sleeve. The connections between the connector members. Electrical connection is made to the filamentary heater lead II by a pair of lead-in conductors l2 likewise sealed in the press 3. The tube is provided with the usual base It having a pluralityoi base prongs H to which suitable emitting material,

the outer ends of the various lead-in wires are connected, thus establishing the external electrical connection to the electrodes within the envelope.

Heretofore the electrical connector I has been made of a material substantially similar to that from which the cathode sleeve 5 is constructed. This material is ordinarily nickel. Previous considerations as to this connector have been simply that it should be a good electrical conductor so as to make a good electrical connection to the oathode sleeve. I have found, however, that if the connector I4 is made of an electrical conductor which has a substantially lower thermal conductivity than that of the material of which the cathode itself is made, the operation of the tube is substantially improved. For example, if the connector I4 is made of an iron-nickel alloy having substantially 36% nickel, 63% iron, and a very small amount of carbon, the thermionic emission and the mutual conductance of the tube are much higher than those in which the pure nickel is used for the connector Id. The alloy to which I have referred is known in the trade as Nilvar, and has a thermal conductivity of approximately one-seventh that of pure nickel.

improvement in the result which is produced depends upon the lowered thermal conductivity of this alloy. Due to the difference in thermal conductivity along the system which occurs at the point of connection between the connector l4 and the cathode sleeve 5, the entire cathode sleeve can be maintained at a relatively high and uniform temperature, and at the same time a sharp drop in temperature can occur at said connection. Of course other electrical conductors having a substantially lower order of thermal conductivity than nickel could likewise be used. For example, other nickeliron alloys having varying amounts of nickel and iron could be used. One alloy in particular, namely that having 42% nickel and about iron, has been found to be particularly useful in this connection. Such an alloy welds very readily to nickel conductors, and otherwise produces the beneficial results mentioned above. Also nickel silicon alloys consisting of nickel with a relatively small percentage of silicon therein likewise possess the requisite low thermal conductivity and good electrical conductivity to produce the novel results which are inherent in my invention. In these alloys the silicon content may be of the order of 3% to 5% silicon, although higher silicon content may be used. It appears that the addition of the silicon to the nickel in this alloy lowers the thermal conductivity to the requisite degree without interfering too greatly with the electrical conductivity or with the ability of this alloy to be welded to nickel electrodes and nickel conductors.

Although I have described my invention as being applied to a connector for an indirectlyheated cathode, I have also found that connectors of this kind can be used for other electrodes, such as, for example, an anode in certain cases with very beneficial results. An arrangement of this kind is shown in Figs. 3, 4 and 5 which illustrate a double anode rectifier tube. This tube is made with a glass envelope l8, which It appears that the in Fig. 3 is shown broken away so that the structure within said envelope can more readily be seen. The envelope i8 is provided with a reentrant stem I9 having a glass press 20 at the upper end thereof. This press 20 supports a pair of anodes 2| within each of w "ch is supported a filamentary thermionic cathode 22. The electrode assembly is supported primarily from a pair of supporting standards 23 sealed in the stem I. The standards 23 support an upper insulating spacer 24 and a lower insulating spacer 25. 5 Each anode 2| is provided with a flange 26 each of which is connectedto an anode standard 21 and likewise is received between the upper and lower insulating spacers 24 and 25, whereby the anodes 2| are supported in position. The anode standards 21 project through the spacers 24 and -25; To the lower end of each anode standard 21 is electrically welded an anode connector 28, which in turn is connected to an anode lead-in conductor 29 sealed in the press 20.

In order to support the filamentary cathodes 22, the upper insulating spacer 24 supports a pair of posts 30 to each of which is welded a resilient hook 3| which supports the upper end of the associated filamentary cathode 22. The lower insulating spacer 25 has supported thereon a pair of posts 22 to which is welded an intermediate connector 33. The opposite ends of this intermediate connector 33 are welded respectively to an end of each of the filamentary cathodes 22. The other end of each cathode 22 is connected to a conductor 34 which in turn is welded to an adjacent standard 23. These standards 23 therefore serve as the lead-in conductors for the two filamentary cathodes 22 connected in series.

The tube is provided with the usual base 35 having a plurality of contact pins 36 to which the lead-in conductors are connected, and in this way an external electrical connection is made to the electrodes.

The connectors 28 in the arrangement shown in Figs. 3, 4 and 5 are made of the same material as that described in connection with the connector H in Figs. 1 and 2. The anodes 2| during operation are raised to a relatively high temperature, due to the passage of an electrical discharge in the tube and also due to heat radiated from the filamentary cathodes 22. The anodes 2| are relatively massive, and therefore possess a considerably high heat capacity. Heretofore difficulty has been encountered in excessive amounts of heat travelling from the anodes through the connectors 28 to the press 20. This excessive amount of heat has raised the temperature of the press 20 to a point at which the glass becomes partially conductive. Under these conditions the voltages impressed upon the leadin wires have caused electrolysis of the glass which has produced a premature failure of the ,5 tube, due to air leaks along the wires wherethe glass has been electrolyzed. In a device made in accordance with my invention, the anodes 2| and the standards 21 are usually made of nickel, while the connectors 28 are made of a special (50 material having a considerably lower order of magnitude of thermal conductivity. Under these conditions a large temperature gradient can exist between the standards 21 and the lead-in conductors 29 without an excessive amount of heat flowing through the connectors 28. Under these conditions the stem 20 remains cool and electrolysis does not occur. Such an arrangement makes for a greater utilization of the tube structure inasmuch as larger discharge currents can be carried, thereby raising the anodes to higher temperatures without introducing the danger of damaging the tube.

Of course it is to be understood that my invention is not limited to the particular details 01' construction as set forth above inasmuch as many equivalents will suggest themselves to those skilled in the art. The invention sets forth certain broad principles which when utilized accomplish the novel results which I have described.

' It is accordingly desired, therefore, that the appended claims be given a commensurate with within this art.

What is claimed is:

1. An electrical space discharge device comprising a sealed enevelope containing a plurality of electrodes, one of said electrodes being heated to a relatively high temperature during operabroad interpretation the scope of the invention tion, lead-in conductors for said electrodes sealed through the wall of said envelope, and an electrical connector made of a material of a lower order of thermal conductivity than the material of said heated electrode interposed between and electrically connecting said heated electrode and its associated lead-in conductor, saidconnector as a whole having a lower order of thermal conductivity than said heated electrode.

2. An electrical space discharge device comprising a sealed envelope containing an anode and a thermionic cathode, lead-in conductors for said electrodes sealed through the wall of said envelope, and an electrical connector made of a material of a lower order of thermal conductivity than the material of said cathode interposed between and electrically connecting said cathode and its associated lead-in conductor, said connector as a whole having a lower order of thermal conductivity than said cathod 3. An electrical space discharge device comprising a sealed envelope containing an anode and a thermionic cathode comprising a cathode sleeve coated with emitting oxide and a filamentary heater within said sleeve, lead-in conductors for said electrodes sealed through the wall of said envelope, and an electrical connector made of a material of a lower order of thermal conducinterposed between and electrically connecting said cathode sleeve and its associated lead-in conductor, said connector as a whole having a lower order of thermal conductivity than said cathode.

4. An electrical space discharge device comprising a sealed envelope having a glass wall containing a plurality of electrodes, one of said electrodes having a relatively high heat capacity and being heated to a relatively high temperature during operation, lead-in conductors for said electrodes sealed through said glass wall, and an electrical connector made of a material of a lower order or thermal conductivity than the material 01' said heated electrode interposed between and electrically through the wall or said envelo connecting said heated electrode and its associated lead-in conductor, said connector as a whole having a lower order oi. thermal conductivity than said heated electrode.

5. An electrical space discharge device comprising a sealed envelope containing a plurality of electrodes, one of said electrodes being heated to a relatively high temperature during operation, lead-in conductors for said electrodes sealed through the wall of said envelope, and an electrical connector consisting of an alloy of nickel and iron, having a lower order of thermal conductivity than the material of said heated electrode, interposed between and electrically connecting said heated electrode and its associated lead-in conductor, said connector having a lower order of thermal conductivity than said heated electrode.

6. An electrical space discharge device comprising a sealed envelope containing a plurality of electrodes, one of said electrodes being'heated to a relatively high temperature during operation, lead-in conductors for said electrodes sealed through the wall of said envelope, and an electrical connector consisting of an alloy of nickel, containing more iron than nickel, and having a lower order of thermal conductivity than the material of said heated electrode interposed between and electrically connecting said heated electrode and its associated lead-in conductor, said connector having a lower order of thermal conductivity than said heated electrode.

7. An electrical space discharge device comprising a sealed envelope containing a plurality of electrodes, one 01 said electrodes being heated to a relatively high temperature during operation, lead-in conductors for said electrodes sealed through the wall of said envelope, and an electrical connector consisting of an alloycomposedsubstantially solely of nickel and silicon interposed between and electrically connecting said heated electrode and its associated lead-in conductor, said connector having a lower order of thermal conductivity than said heated electrode.

8. An electrical space discharge device comprising a sealed envelope containing a plurality of electrodes, one of said electrodes being heated to a relatively high temperature during operation, lead-in conductors for said electrodes sealed and an electrical connector consisting 01 an alloy composed substantially solely of nickel and a small percentage of silicon interposed between and electrically connectingv said heated electrode and its associated lead-in conductor, said connector having a lower order of thermal conductivity than said heated electrode.

THOMAS H. BRIGGS, JR. 

